An Introduction to Hydrofluoric Acid

What is Hydrofluoric Acid?

Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. It is a precursor to almost all fluorine compounds, including pharmaceuticals such as Prozac, diverse materials such as Teflon, and elemental fluorine itself. It is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. Its ability to dissolve glass has been known since the 17th century.

Hydrofluoric Acid Awareness

It has a high reactivity toward glass and moderate reactivity toward many metals, hydrofluoric acid is usually stored in plastic containers.

Hydrogen fluoride gas is an acute poison that may immediately and permanently damage lungs and the corneas of the eyes. Hydrofluoric acid is a contact-poison with the potential for deep, initially painless burns and ensuing tissue death. It interferes with the metabolism of calcium in the body. The acid may also cause systemic toxicity and eventual cardiac arrest and fatality, after contact with as little as 160 cm2 (25 square inches) of skin, so it is a substance not to be messed with!

What are the properties of Hydrofluoric Acid?

It looks innocent….. Just like water…. BUT….

The chemical, physical and toxicological properties of Hydrofluoric Acid (HF) make handling extremely hazardous. Hydrofluoric acid (HF) can exist as:

  • A colourless gas
  • A fuming liquid
  • Can be dissolved in water

All forms, including the vapour, cause Hydrofluoric Acid Safetysevere burning to living tissues. It dissolves glass, enamels, silicon, pottery, concrete, rubber, leather, ferrous and non-ferrous metals. It also reacts with metals to produce explosive hydrogen.

It dissolves glass, so must be stored in polyethylene, polypropylene, Teflon, wax, lead or platinum.

HF is NOT a strong acid compared to HCl, H2SO4, HNO3 (i.e. it does not fully ionise in dilute solutions), and it is made up of very small particles, which makes it very hard to filter.

The hydrofluoric acid reacts in contact with other substances:

  • Glass, concrete, other materials containing siliconHydrofluoric Acid Experiment
    • Yields tetrafluoride gas
    • Pressure build up can rupture glass containers
  • Carbonates, sulphides, cyanides
    • Yields toxic gas including hydrogen cyanide
  • Alkalis, some oxides
    • Causes strong exothermic reactions
  • Common metals
    • Yields explosive hydrogen gas
  • Highly corrosive to many materials
    • Considerable heat and violent reaction when added to water

How is Hydrofluoric Acid used?

HF has a number of industrial and research applications, it is used for:

  • Manufacture of electronic components
  • Etching glass
  • Making semiconductors
  • Pickling of metals
  • Alkylation in the refining oil
  • Manufacturing refrigerants
  • Dissolving rock samples for analysis

Is Hydrofluoric Acid harmful?

In addition to being a highly corrosive liquid, hydrofluoric acid is also a powerful contact poison. As a result of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident, and this can provide false reassurance to victims, causing them to delay vital medical treatment. Despite having an irritating odour, HF may reach dangerous levels without an obvious odour. HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury. Symptoms of HF exposure include irritation of the eyes, skin, nose, and throat, eye and skin burns, rhinitis, bronchitis, pulmonary oedema (fluid build-up in the lungs), and bone damage.

The fluoride ions in HF are both acutely and chronically toxic, causing:

  • Severe and penetrating burns
  • Respiratory irritation
  • Severe eye damage
  • Pulmonary oedema
  • Unbelievable levels pain
  • Corrosion and necrosis of skin
  • Cardiac arrest

The Fluorine ions (F-) bind with Calcium (Ca) and the subsequent formation of insoluble calcium fluoride causes a rapid drop in the body’s available calcium and severe pain associated with tissue toxicity. Exposures can lead to hypocalcaemia, causing numbness, muscle spasms, seizures, confusion, or cardiac arrest.

How do we treat for exposure to Hydrofluoric Acid?

The key word is QUICKLY! Exposure to hydrofluoric acid is a serious, and potentially life-threatening situation for the victim, and highly hazardous for those treating the casualty. Clear understanding and knowledge of the properties of HF are vital for the safe and successful treatment of any exposure.

 

 

To book a course increasing your awareness of, and ability to safely treat the effects of hydrofluoric acid, or for further information please visit this page, call us on 01684 851290 or email info@universalsafetysolutions.co.uk.

 

Warren Ingham-Barrow

Senior Consultant

Universal Safety Solutions Ltd.